The invention relates in general to battery technology and more particularly to techniques for extending the operational life of batteries such as disposable and rechargeable batteries. Most consumer electronic equipment use batteries. Batteries are classified in terms of primary batteries of dry cells, secondary batteries and rechargeable batteries. Many of electronic equipment are sensitive and need very precise voltages to operate properly. In some cases, if the battery supplying voltage to electronic equipment drops too low, not only does the equipment provide unreliable output, but the low voltage could also damage the equipment. As such, many manufacturers of electronic equipment include circuitry that detects battery voltage levels and if the voltage level drops below a certain level, the circuit would turn itself off. As an example, a fresh unused AA battery provides 1.5V. Over time, as the battery charge is consumed by the equipment that utilize the battery, the battery voltage starts to drop.
Some electronic equipment that use disposable batteries, such as AA batteries, are designed to stop operating when the battery voltage drops by 10% or so. That means when the voltage of an AA battery drops to about 1.4V or 1.35V, the battery is no longer useable by the equipment and has to be replaced with a fresh battery. Thus, the entire voltage range between 0V to 1.35V is wasted, resulting in significant inefficiency. This is akin to the scenario where only 10% of a soda bottle is consumed, as a matter of routine, and the rest discarded. This clearly would be very wasteful and inefficient.
Another factor impacting the cost of batteries is that some of the material used in manufacturing batteries are difficult to mine and in some cases are considered rare earth materials. The price of these materials have been on the rise since some are only found in countries like China, and China has started limiting the export of these materials.
In addition to the adverse economic impacts of battery inefficiencies, there are significant environmental impacts. There are about 3 billion batteries sold every year. Batteries pose a special environmental risk because they contain toxic material that can find their way into our natural resources such as ground water. They also are not biodegradable. Many nations as well as municipalities have laws and local ordinances about recycling of batteries. Furthermore, the carbon footprint associated with manufacturing and distribution of batteries raises concerns. The process of mining these materials, putting them in the batteries, packaging the batteries, and shipping them all over the world takes a lot of energy and generates a lot of greenhouse gases. Thus, improving the use efficiency of batteries provides significant economic as well as environmental benefits.
Thus, there is a need for techniques that improve the efficiency of batteries such as disposable and rechargeable batteries.